/rant on!
This bug blindsided me so bad that I am reloading the save to try to work around it. But I did save the gifs I took of the fight showing off exactly what happened, so hopefully others who have not experienced it yet will be forewarned...
Here we have 4 squads of dwarfs rush out to defend the fort against a force of about 34 white tigermen (fortress defense). The group they rush has about 25 in it. No problems so far.
Here we see the trouble setting up. All dwarfs have been ordered to station beyond where the left hand group of tigermen stand. instead, they stack on top of three tiles and stand there. Sound Sense is flooded with sounds of terror from my dwarfs. Meanwhile, marksdwarfs show up and begin shooting at the enemy. A spearmaster who was not involved in the main fight spies them and rushes them as well
The lone spearmaster reaches them and does his best to fight, but is soon knocked out. More crossbowmen arrive and shoot, but crossbows just aren't the railguns they were in DF2012. Meanwhile, the 27 melee dwarfs involved in the first scuffle are STILL hanging out on three tiles. They ignore new station orders. They ignore kill orders. A new spear master, injured in a previous fight, walks up from the back.
The lone unconscious spear master is rescued by 2 spearmasters who both did not fight in the main battle. Meanwhile, the 27 others are still standing still, being terrified. Based on soundsense, they are making comments about how fleeting life is, banishing terror, or expressing horror at death. I cancel orders on one group, and they immediately try to run back inside! I tell that group to station near the fight, and they ignore it. I tell them to KILL the group, and they ignore it. I wind up locking them outside the fort, at which point they STOP and do NOTHING.
The finale. The final tigermen die to the three spear masters and the marksdwarfs taking potshots. As the last tigermen dies, the remainder of the military snaps out of it and rushes to the scene of the battle.
I have encountered this before, though never for such a long amount of time. They will fight one fight, then stand there stupidly until they actually see another target or have their current orders canceled.
I think when I redo this fight (the lone spear master suffered some nasty injuries) Ill keep one group in reserve and send them in if the main group freezes like that again.